How to Find the Length of List in Python?

How to Find the Length of List in Python?

Introduction- Software developers and data scientists all over the world have a great demand for Python. Lists are an indispensable part of daily Python programming. All Python users should understand their profits and operations which is essential and is always an advantage. A list in Python is an ordered and changeable collection data type. The list can also have duplicate entries. 

A list is implemented in Python to store sequences of various data types. However, there are six data types in Python that can store sequences, but the most common and reliable type is a list. One of the very similar features such as the list is Arrays. The difference between lists and arrays is that they provide a more compact and efficient way to store large numbers of items. 

Although matrices involve numerical operations, there is no need to perform direct mathematical activities on lists.

List being an integral part of Python day-day programming has to be learned by all the python users and having a knowledge of its utility and operations is essential and always a plus.

If you are a new IT or software professional, or a data professional, you should be proficient in this programming language.

Most refresher courses are designed to familiarize candidates with Python by using the basics of programming, statistical tools, and predictive analysis as part of the main project and coursework.

How to find the length of a list in python? 

Calculating the length or size of the list is similar to finding the total number of items present in the list.  For example, if  list1: list1 = [5,4,7,2,9,6], then the length of list lis1 is 6. Because the total number of elements or elements is 6.

There are two basic and most commonly used methods for finding the length of a list in Python: 

- Len() method 

- Naive method

- Using The __len__() Method

- Using length_hint()

- Using Python for loop to get length method

1. Len() Method:

There is a built-in function called len() to get the total number of elements in a list, tuple, array, dictionary, etc. The len() method accepts a parameter in which you can provide a list and return the length of the list. 

The len() method is one of the most widely used and convenient methods for finding the length of a list in Python. This is the most traditional technique used by all programmers today.

The built-in len() method in Python is widely used to calculate the length of any type of sequential data. Calculate the number of elements or the number of elements of the object, and return the same value as the length of the object. 

Therefore, we can directly obtain the length of a list and pass it to the built-in method len().

The syntax of the len () function 

The basic syntax of the len () function in Python is as follows: 

len (List_name) 

Parameters: 

Parameters - List_name 

Description - The length of the list will be calculated. 

Return value - will return an integer value that is the length of the list. 

Definition list - the list is enclosed in brackets

Example:- len (list) 

The List parameter is a list to count the number of elements. Returns the number of items in the list.

1. ListName = ["Hello", "Alexa", 1, 2, 3]
2. print ("Number of items in the list = ", len(ListName))

Output:5

2. Naive Method:

The len(list) method The len() method is the most widely used method for finding the length of a list in Python. But there is another basic way to provide the length of the list. 

In the Naive method, you only need to loop and increment the counter to the last item in the list to know its count. This is the most basic strategy that can be used without other effective techniques.

In other words, In this Naive method, we use the count variable to find the number of items in the list. It is a technique that uses an established (para) control loop format. In this set, the controlled loop does not follow any conditions, it only follows the length of the set. To do this, we simply add 1 to the value of the count. Finally, it returns the number of elements.

Example:

1. ListName = [ "Hello", "Alexa", 1,2,3 ]
2. print ("The list is : " + str(ListName))
3. counter = 0
4. for i in ListName:
5. counter = counter + 1
6. print ("Length of list using naive method is : " + str(counter))

Output: The list is : ["Hello", "Alexa", 1,2,3]

The length of a list using the naive method is: 5

It's about finding the length of the list in Python. The len () method is the most popular method. However, you can also use the basic method to find the length with the help of the naive method. 

3. Using The __len__() Method:

The __len __ () method is another built-in Python method that can be used to find the length of a list. 

Although the len () and __len __ () methods appear similar, there is the slightest difference between the two. 

When the len () function is called, it calls the __len __ () method internally, which returns the count of elements in the sequence, which is a list. Also, we can directly call the __len __ () method.

Example:

# Python program to find length of list 

# Use __len __() method 

# Initialize the list to find the length 

MyList = [`Red`,`Yellow`,`Green`,`Orange`,`Pink `] 

Length = MyList. __ len __() 

print("The length of the list is: ", Length) 

Output: 

The length of the list is: 5

4. Using length_hint():

This technique is a little known technique for finding the length of a list. This special method is defined in the operator class and can also indicate that it is not. Items present in the list.

Definition - Returns with the length of iterable items. 

Syntax - Operator.length_hint()

Parameters - objective, iterable

Example:- Demonstrating finding length of list using len() and length_hint()

# Python code to demonstrate

# length of list

# using len() and length_hint

from operator import length_hint

# Initializing list 

test_list = [ 1, 4, 5, 7, 8 ]

# Printing test_list

print ("The list is : " + str(test_list))

# Finding length of list 

# using len()

list_len = len(test_list)

# Finding length of list 

# using length_hint()

list_len_hint = length_hint(test_list)

# Printing length of list 

print ("Length of list using len() is : " + str(list_len))

print ("Length of list using length_hint() is : " + str(list_len_hint))

Output :

The list is : [1, 4, 5, 7, 8]

Length of list using len() is : 5

Length of list using length_hint() is : 5

5. Using Python for loop to get length method: 

To find the length of a list in Python, using the for loop is considered a traditional technique or a naive method, as shown below: 

Declare a counter variable and initialize it to zero. 

Use a for loop to loop through all data items. After each item is found, the counter variable is incremented by 1. 

In this way, the length of the array will be stored in the counter variable, because the variable will represent the number of items in the list.

Example: inp_lst = ['Python','Java','Kotlin','Machine Learning','Keras']

size = 0

print("Length of the input string:")

for x in inp_lst:

size+=1

print(size)

Output:

Length of the input string: 5

List in Python:

A list is implemented in Python to store sequences of various data types. However, there are six data types in Python that can store sequences, but the most common and reliable type is a list.

A list is defined as a collection of different types of values ​​or elements. Items in the list are separated by commas (,) and enclosed in square brackets []. 

It  is defined as follows:

list1 = ['alexa', 'python', 2019];

list2 = [1, 2, 3, 4, 5 ];

list3 = ["a", "b", "c", "d"];

The execution time of various methods to find the length of the list in python: 

•  len(): 0.0 (seconds) 
• __len__() : 0.0 (seconds)
•  length_hint(): 0.00046 (seconds) 
•  Naive method: 0.00057 (seconds) 

Therefore, len() is the best way to find the length of the list in python and can be used because it has the shortest execution time of all available methods.

Conclusion:

Python List is now known to be a variable ordered sequence. It can contain heterogeneous and homogeneous elements. It is a widely used data structure in Python. For traversal and other operations on the list, sometimes it is necessary to find the length of the list. It's about finding the length of the list in Python. The len () method is the most popular method. You can clearly see that the time spent is naive >> length_hint ()> len (), so len () is the best option. 

However, you can also use the basic method to find the length of the list in Python with the help of the naive method. This information on measuring the length of a list in Python is one of the most basic things you should do as a beginner. So, use the steps above to improve our programming skills and stay curious to learn more! 

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